Rehydrogenation of hydrogenated fatty acids



United States Patent 3,271,410 REHYDROGENATIQN 0F HYDROGENATED FATTYACHDS Lucien J. Cagneron, Pekin, IlL, and Eugene A. Skaradzinski,Minneapolis, Minn, assignors to Archer-Daniels- Midland Company,Minneapolis, Minn., a corporation of Delaware No Drawing. Filed July 19,1965, Ser. No. 473,204 11 Claims. (Cl. 260-400) This application is acontinuation-in-part of Serial No. 218,125, filed August 20, 1962, nowabandoned.

The present invention relates to the preparation of fatty acids havingimproved quality characteristics. In one aspect, this invention concernsthe rehydrogenation of hydrogenated tallow fatty acids using a palladiumcatalyst during the rehydrogenation step.

In the ordinary preparation of fatty acids for commercial consumption,hydrogenation of the fatty aicds is frequently employed. Typically, thishydrogenation is carried out until the iodine value of the fatty acid isreduced below 10. Frequently, the iodine value is reduced below 5, e.g.,below 2. However, the non-fat constituents commonly present in fattyacids (generally known as unsaponifiable matter) are not completelyreduced by hydrogenation. These non-fat portions are primarilyresponsible for poor color stability, objectionable odor, and poorstability towards concentrated sulfuric acid, ammonia, and aminesfrequently encountered with fatty acids. Consequently, fatty acids ofhigh quality have heretofore been produced by either treating the fattyacids prior to hydrogenation (or subsequent to hydrogenation) by suchtechniques as solvent crystallization, solvent leaching, acid treatment,alkali refining, and the like. Such processes can produce fatty acidshaving improved qualities, but such processes are sometimes wasteful ofmaterials, and may consume a great deal of time and labor. Further,merely continuing the original hydrogenation process, as such, isgenerally believed to produce no significant improvement.

We have now discovered, and this discovery forms one basis for thepresent invention, that fatty acids having improved qualitycharacteristics can be conveniently produced by rehydrogenatingconventionally hydrogenated fatty acids. These results are particularlysurprising since little hydrogenation (as evidenced by the reduction iniodine value) appears to take place during rehydrogenation. In anyevent, the net result of rehydrogenation is the production of fattyacids having improved color stability, improved odor, and improvedstability towards concentrated sulfuric acid, ammonia, and amines.

The process of the present invention, in the broad sense, involves therehydrogenation of a catalytically hydrogenated fatty acid ofconventional character at temperatures of from 200 to 500 F. underpressure of from 10 p.s.i.g. to 5,000 p.s.i.g. for from five minutes toabout hours in the presence of a catalytic amount of hydrogenationcatalyst. Preferably, the hydrogenated fatty acid to be rehydrogenatedis freed of its initial hydrogenation catalyst. For maximum improvementand for extending the catalyst life, the initial hydrogenated fatty acidis preferably distilled before rehydrogenation.

It should be noted that the present invention is directed to therehydrogenation of a substantially completely hydrogenated fatty acid.Thus, the process of the present invention can be readily distinguishedfrom prior art processes which, for example, have involved thehydrogenation of a triglyceride in a two-step fashion. In such prior artprocesses, the effect of the multiple hydrogenat-ion was merely toapproach that degree of hydrogenation which now can be commerciallyobtained, in most instances, in a single hydrogenation step. For

3,271,410 Patented Sept. 6, 1966 such a non-analogous prior art process,see US. 2,307,065.

The fatty acids which can be used in the process of the presentinvent-ion include the C to C fatty acids, individually or as mixture-s.Typically, C to C fatty acids will be processed according to the presentinvention. Such fatty acids include the fish oi'l fatty acids, tallowfatty acids, tall oil acids, oleic acid, and the like. The manner ofhydrogenating the fatty acids, in the first instance, is not critical,and we have successfully employed our process using hydrogenated fattyacids which are commercially available. However, we have obtainedimproved results by hydrogenating fatty acids, in the first instance,using our process conditions. This seems particularly true wherepalladium (in one form or another) is used as the hydrogenationcatalyst.

The temperatures used for the rehydrogenation step will typically rangefrom 225 to 450 F. We generally prefer to use a temperature within therange of 350 to 450 F., e.g., 375 F. As regards pressure, therehydrogenation can be effected at pressures within the range of 10p.s.i.g. to 5,000 p.s.i.g.

We generally prefer to employ a pressure within the range of 50 p.s.i.g.to 2,500 p.s.i.g. Our rehydrogenation process can be conducted on abatch or continuous basis and, if desired, can be integrated with theoriginal bydrogenation process. When operating a batch process, we havefound pressures of from 300 to 500 p.s.i.g., e.g., about 400 p.s.i.g.,to be satisfactory. In a continuous system, we prefer to employpressures of from 750 p.s.i.g. to 2,000 p.s.i.g., e.g., about 1,500p.s.i.g.

The catalysts useful in practicing the present invention are thehydrogenation catalysts. Suitable hydrogenation catalysts include thenoble metals, the noble metal oxides, nickel, activated or promotednickel, copper, cobalt, copper chromite, and the like. These catalystscan be used alone or in combination. They can be used in such diverseforms as powders, pellets, rods, and the like. They can be used free orsupported on alumina, refractory oxides, silica, carbon, kieselguhr, andthe like. Palladium, in any one of its ordinary catalytic forms, is thepreferred catalyst. Particularly preferred as a catalyst is palladiumsupported on carbon.

The amount of catalyst used will be a catalytic amount, usually withinthe range of from 0.001 to 1.0 percent by weight (neglecting the Weightof the support) based on the amount of fatty acid to be treated.Commonly, the amount of catalyst will be within the range of from 0.001to 0.15 weight percent, on the same basis. When using the preferredcatalyst (i.e., palladium), we prefer to use, sufiicient commercialcatalyst (e.g., palladium on carbon) to provide about 0.01 weightpercent palladium, per se.

As previously indicated, any conventional hydrogenation catalyst can beused in a conventional manner in the first or original hydrogenation.This original hydrogenation is ordinarily carried out to the lowesteconomically feasible iodine value. Typically, this would be an iodinevalue of 10 or below. For optimum results, the catalyst used in thefirst hydrogenation should be removed (e.g., as by filtration), althoughthis is not absolutely necessary. However, it is desirable. This isparticularly true where a palladium catalyst has not been used in thefirst hydrogenation step (but is used in the second step) since removalfacilitates the reuse and recovery of the palladium catalyst.Distillation of the fatty acids after rehydrogenation is especiallydesirable since it allows maximum benefits to be derived from therehydrogenation.

The present invention will be further understood by reference to thefollowing specific examples, which include a preferred embodiment.Unless otherwise indicated, all parts and percentages are by weight.

Example I.A split, bleachable, fancy tallow acid 3 was hydrogenated at375 F. and 400 p.s.i.g. for a period of 5 hours using 0.2% of acommercial catalyst (5% palladium lOIl carbon), thereby providing 0.01%palladium, per se. After hydrogenation, the catalyst was removed byfiltration and the hydrogenated tallow acid was rehydrogenated at 375 F.and 400 p.s.i.g. for 2 hours. Again, 0.2% of a 5% palladium on carboncatalyst was used to thereby provide 0.01% palladium. Afterrehydrogenation, the catalyst was removed by filtration and the acidswere distilled. Rehydro genation appreciably improved the odor of thetallow acids. Color improvement is shown in Table I which follows:

TABLE I Lovibond Color Before Rcliy- After Robydrogenation drogcuationOriginal color 5% 4Y0.7 R 2Y-0.0R. Color after 2 hrs. at 205 C Y2.1R7Y0.1R.

Example lI.-Hydrogenated menhaden acids were rehydrogenated at 380p.s.i.g. and 375 F. for 3 hours, using 0.2% of a 5% palladium on carboncatalyst (thereby providing 0.01% palladium). After rehydrogenation hadbeen completed, the catalyst was removed by filtration and the acidswere distilled.

Rehydrogenation caused a noticeable improvement in the odor of theacids. Other improvements in the quality of the acids are shown in TableII, which follows:

Example IlI.Menhaden fatty acids were hydrogenated at 400 F. and 200p.s.i.g. for 5 hours using 0.1% of a reduced nickel catalyst. The acidswere substantially completely hydrogenated (i.e., an iodine value below10). The hydrogenated menhaden acids were then rehydrogenated withoutfiltration at 375 F. and 1500 p.s.i.g. for 5 hours using 0.15 of anickel catalyst. After rehydrogenation, the acids were distilled.

The odor of the fish acids, after rehydrogenation, was appreciablyimproved. The additional processing had provided a fresh, clean odor ascompared to the smell of the raw and initially hydrogenated product.Improvement in other qualities are shown in Table III, which follows:

Example lV.Fish oil fatty acids (the same as used in Example III) werehydrogenated as described in Example III. The hydrogenated fatty acidswere then fil- TABLE IV Before Rehy- After Rehydrogenation drogenatiouOriginal color (Lovibond) 5YO.GR 0.5Y0.1R. Colorgfter 2 hrs. at 205 C.(Lovi- 30Y-3R 2.5Y0.5R.

on Stability to cone. sulfuric acid 11 3.

(Barrett color).

Example V.Fish oil fatty acids were hydrogenated with a nickel catalystin the manner described in Example III. After hydrogenation (which wassubstantially complete), the fatty acids were filtered to remove thecatalyst. Then, the hydrogenated fish oil fatty acids wererehydrogenated at 376 F. and 1500 p.s.i.g. for 5 hours using 0.15%copper chromite catalyst. After rehydrogenation, the acids weredistilled. Improvements in the quality characteristics of the fattyacids are set forth in Table V, which follows:

TAB LE V Before Rehy- After Rehydrogenation drogeuation Original color(Lovibond) 5Y0.6R 1Y0.1R. 0%101 after 2 hrs. at 205 C. (Lovi- 30Y-3R0Y-1.3R.

cnc Stability to cone. sulfuric acid 7.

(Barrett color).

Example VI.A bleachable fancy tallow was batch split with water and thenhydrogenated with a nickel catalyst in a conventional manner to therebyproduce hydrogenated tallow fatty acids having an iodine value of 1.2.After filtering the hydrogenated tallow fatty acids to remove the nickelcatalyst, the fatty acids were rehydrogenated in a batch autoclave(using different catalysts in different runs) at 375 F. and 1500p.s.i.g. of hydrogen for 2 hours. After rehydrogenation, the fatty acidswere filtered to remove the catalyst and then distilled. Theeffectiveness of the rehydrogenation and a comparison of varioushydrogenation catalysts is set forth in Table VI which follows:

From the foregoing examples and description, it is clear that therehydrogenation of a normally or conventionally hydrogenated fatty acid,especially with the use of a palladium catalyst, can significantlyimprove odor,

stability to heat, and stability to concentrated sulfuric acid, ammonia,and amines.

Having described the present invention with a certain degree ofparticularity, it will be realized that numerous minor changes andvariations, falling within the spirit and scope of this invention, willbecome obvious to those skilled in the art. It is not intended that thisinvention be limited to any of the materials which have been mentionedas specific examples nor by any of the specific proportions which havebeen given for the sake of illustration, but it is intended to claim allnovelty inherent in the invention, as well as all obvious modificationsand variations thereof.

What is claimed is:

1. The process of improving the quality of a catalytically-hydrogenatedfatty acid which comprises catalytically rehydrogenating saidhydrogenated fatty acid at a temperature of from 200 to 500 F. and at apressure of from p.s.i.g. to 5000 p.s.i.g.

2. The process of claim 1 wherein said hydrogenated fatty acid has aniodine value below 10, wherein said pressure is from 50 to 2500p.s.i.g., and wherein said temperature is from 225 to 450 F.

3. The process of claim 2 wherein said rehydrogenation is conducted as abatch process and wherein said pressure is from 300 to 500 p.s.i.g.

4. The process of claim 2 wherein said rehydrogenation is conducted on acontinuous basis and wherein said pressure is from 750 to 2000 p.s.i.g.

5. The process of claim 2 wherein rehydrogenated fatty acids aresubsequently distilled.

6. The process of rehydrogenating a catalyticallyhydrogenated long chainfatty acid which comprises the steps of adding to said hydrogenatedfatty acid a catalytic amount of from 0.001% to 1% of palladium byweight based on the weight of said fatty acid, and further hydrogenatingsaid hydrogenated fatty acid at a temperature of from 200 to 500 F. fora period of from 5 minutes to 5 hours under a pressure of from about 380to about 400 p.s.i.g.

7. The process of rehydrogenating a tallow fatty acid which has hencatalytically hydrogenated with palladium which comprises the steps ofadding to said hydrogenated tallow fatty acid a catalytic amount of from0.001% to 1% of fresh palladium based on the weight of said fatty acid,and further hydrogenating said hydrogenated tallow fatty acid at atemperature of about 375 F. at a pressure of about 400 p.s.i.g. for aperiod of from 5 minutes to '5 hours.

8. The integrated process of rehydrogenating a catalyticallyhydrogenated C to C fatty acid having an iodine value below 5 whichcomprises the steps of removing hydrogenation catalyst from saidhydrogenated fatty acid, adding to said hydrogenated fatty acid acatalytic amount of a palladium catalyst and further hydrogenating saidhydrogenated fatty acid at a temperature of from 350 to 400 F. for aperiod of from 5 minutes to 5 hours under a pressure of from to 2500p.s.i.g.

9. The process of claim 8 wherein the hydrogenation catalyst used toinitially hydrogenate said fatty acid is also a palladium catalyst.

10. The process of claim 8 wherein said palladium catalyst is palladiumon carbon.

11. The process of claim 8 wherein the rehydrogenated fatty acids aresubsequently distilled.

CHARLES B. PARKER, Primary Examiner. ANTON H. SUTTO, Assistant Examiner.

1. THE PROCESS OF IMPROVING THE QUALITY OF A CATALYSTICALLY-HYDROGENATEDFATTY ACID WHICH COMPRISES CATALYTICALLY REHYDROGENATING SAIDHYDROGENATED FATTY ACID AT A TEMPERATURE OF FROM 200* TO 500*F. AND AT APRESSURE OF FROM 10 P.S.I.G. TO 5000 P.S.I.G.